Imagine taking the cardboard tube from a roll of paper towels, and affixing a lot of seeds to the inside of the tube. Then repeat the procedure with many other tubes, and glue them together. Suspend all the tubes from a board, so they hang downward--then wait for the seeds fall out. Somewhere along the long line of natural history, the boletes decided that this would be the most successful way to survive. Their caps look like the caps of the gilled mushrooms (a group that decided to hang seeds from sheets of cardboard, instead)--but, on the underside of the cap, there are tubes instead of gills. The tubes are so tightly packed that, from below, one sees only a pore surface composed of the openings of the tubes, looking rather like the surface of a sponge.

With very few exceptions, boletes are mycorrhizal partners with trees, and can be found in forest and urban ecosystems across our continent, wherever ectomycorrhizal trees are present. Some boletes are very picky about their mycorrhizal partners, while others seem to be able to associate only with groups of related trees--and still others may be able to associate with very diverse trees (although we may discover, as molecular study of the boletes evolves, that this last group is not nearly as big as we once thought).

There are a great many species of boletes, and identifying them ranges from relatively easy to profoundly difficult. In most cases you will need to have fresh mushrooms in front of you in order to be successful--preferably, specimens representing young and mature mushrooms. The morphology of a bolete's stem is often a good starting place for identification: look for scabers, glandular dots, or reticulation--and note the color of the basal mycelium. Other morphological features to examine carefully include the cap surface, the pore surface and tubes, the presence or absence of a veil, and the flesh. Many boletes have surfaces and/or flesh that discolor blue (or another color) when bruised or sliced. You will also frequently need to have a spore print available. In a few cases, odor or taste can be important. Chemical reactions can be very useful in identifying boletes; placing drops of ammonia, KOH, and iron salts on the cap surfaces and flesh of boletes can sometimes produce distinctive color reactions. Microscopic analysis of boletes is often required for identification; important characters include the morphology of spores and the pileipellis, along with cystidia in the tubes and on the stem. Finally, since boletes are mycorrhizal, noting what kind of tree is "hosting" your bolete can also be important information in the identification process.

At one time nearly all boletes were placed in the genus "Boletus." If you ask me, mycology should seriously consider returning to this strategy (at least for those genera now placed in the Boletinae), because what is evolving instead is a ridiculous display of career-making "splitting" based on each newly produced molecular phylogeny. Don't get me wrong; I am all for a naming system that actually reflects the way the organisms evolved and how they are phylogenetically related. I have no problem, for example, with including many of the bolete-related "false truffles," underground blobs, and miscellaneous what-nots in the same genera as the boletes they evolved with, despite their very different appearances. But DNA-based bolete taxonomy has taken the opposite route from, say, Cortinarius taxonomy, and has decided instead to name a new genus for virtually each new branch on the bolete tree--resulting in genus silliness like "Harrya" and "Sutorius," along with other taxonomic contortions. While contemporary bolete phylogenies make it clear that the traditional genus "Boletus" is entirely incoherent if we are going to have, for example, a "Leccinum" and a "Tylopilus" (all the comprehensive trees being produced these days show species of "Boletus" all up and down the branches, surrounding species from other genera, enabling no logical grouping), the answer to this problem does not have to be the creation of a new bolete genus for every day of the year. Humbly submitted; feel free, of course, to ignore it.

Regardless of how many bolete genera there are and whether the traditional genera (Boletus, Leccinum, Tylopilus, and so on) are "good," identification of the boletes is still greatly facilitated by the traditional characters. In other words, although DNA studies have shown us that we may not be able to justify separating a genus (Tylopilus) on the basis of a pinkish spore print and smooth spores, we can still handily separate a group of mushrooms for identification using these features. Thus the keys below rely on traditional morphological features--but they are, unfortunately, in varying states of "updatedness." Some of the older keys are very unsatisfactory; please accept my apologies and my promise that, when I can, I will revise them.

Bolete appearing partially to severely malformed; tube layer not oriented strictly vertically; spore print not obtainable; often growing submerged or partially submerged in the ground; most species known from western North America.

Veil stretching from the base of the stem to the cap margin when young, collapsing to form a nearly volva-like basal ring; pore surface bruising promptly brown; found under oaks from the Great Lakes to Colorado.

Pore surface shallow and boletinoid; tubes not easily separable as a layer; cap often off-center and irregularly shaped when mature, not slimy; spores ellipsoid; found only under ash in eastern North America or under alder on the West Coast.

Mushroom without clusters of bundled cystidia; not having two or more of the non-microscopic features above.

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Pore surface frequently (Caucasian) flesh-colored to pinkish when mature (but brown throughout development in a few species); taste often (but not always) bitter; spore print pinkish brown to reddish brown or brown--never olive brown or yellow. (Note: The linked key is out of date and unsatisfactory. My apologies.)

Well defined, conspicuous scabers present on stem (be sure to compare scabers with glandular dots and reticulation if these terms are new to you), often contrasting with the color of the mature stem surface; spore print usually brown to pinkish brown or yellowish brown.

Pore surface not bruising blue (a few exceptions); sliced flesh bluing or not; not usually found near decaying wood; KOH on cap varying; spores not ridged. (Note: The linked key is incomplete, out of date. and unsatisfactory. My apologies.)

Arora, D. & J. L. Frank (2014). Clarifying the butter Boletes: a new genus, Butyriboletus, is established to accommodate Boletus sect. Appendiculati, and six new species are described. Mycologia 106: 464-480.

Baroni, T. J. & E. E. Both (1998). Tylopilus violatinctus, a new species of Tylopilus for North America, with comments on other violaceous colored Tylopilus taxa. Bulletin of the Buffalo Society of Natural Sciences 36: 261-264.

Smith, A. H. & Thiers, H. D. (1971). The boletes of Michigan. Ann Arbor: U Michigan P. 428 pp. An online version of this book is available here, at the University of Michigan Herbarium (URL too long for duplication).